Get a Amex Plat so you have your lounge issue solved. Unlimited DL sky club access too.
In the last 2 years, I noticed that ST offers a lot better value out of YYZ than *A. You get WS/DL/AM for easy access and decent fares to CAN, US, Central America - south america is improving quickly for DL too. There are consistently great fares on KL/AF for Europe, Africa and Central Asia, compared to AC/LH. MU is flooding the market for Asia (sadly, CZ is leaving - they had some great J/PE deals and I dont mind flying them).